ESA Pursues 3-D Imaging Lidar

Lidar operates in the same fashion as radar but with shorter wavelengths since it uses light rather than radio waves. A pulsed laser beam scans targets by measuring the time it takes for the light to bounce back; its shorter wavelength offers more precise measurements — nanometers rather than the centimeters offered by radar.

Separate designs were built in parallel by two consortia, one led by Jena-Optronik of Jena, Germany, and the other by ABSL of Culham, UK.

This car was not snapped with a camera but scanned by a 3-D imaging lidar, the laser equivalent of radar. Image from a 10-second test scan of ABSL’s prototype lidar, combining short- and long-range data. (Image: ESA/ABSL)
The two designs were aimed at different guidance and navigation applications. The German-led unit demonstrates a future rendezvous sensor, while the British-led design is intended to help a lander touch down safely on a planet while detecting and avoiding potential hazards.

The shoebox-sized imaging lidars rely on a steerable scan mirror that flips the laser beam across the target with a highly sensitive light detector to measure the returning beams from several kilometers away.

ABSL prototype lidar, intended to help a lander touch down safely on a planet, detecting and avoiding hazards. (Image: ESA/ABSL)
The imaging lidar could prove useful for the guidance, navigation and control of planetary landers and steering rovers on planetary surfaces, and for assistance in docking the craft in planetary orbit, said Joao Pereira Do Carmo of ESA.

“Terrestrial imaging lidars already exist, typically used for scanning buildings or industrial sites, but they are much too bulky for use in space,” Do Carmo said. “The challenge is to produce a new class of imaging lidar, much smaller and needing less power.”

For missions deeper into our solar system, ESA hopes to use 3-D imaging lidar to build up a complete picture of targets such as boulder-strewn surfaces. It would work much as a stereoscopic imager does, but it would also work in total darkness or blinding sunlight.

ESA’s Automated Transfer Vehicle uses laser ranging sensors to rendezvous and dock with the International Space Station to a positioning accuracy of 2 cm. (Image: ESA TV)
The Imaging Lidar Technology project was supported through ESA’s Basic Technology Research Programme, which is aimed at prototyping promising new engineering concepts, and the newly designed 3-D lidar is expected to assist in the safe landing of ESA’s Lunar Lander in 2019.

The engineers are looking at using new types of detectors and micromechanical optical mirrors to make the lidars smaller.

“It is expected that we can reduce the mass and power consumptions of current commercial imaging lidar systems by at least 70 percent,” Do Carmo said.